Beacon antenna system



ct. 10, 1950 s. B. PKCKLES BEACON ANTENNA SYSTEM Filed March 19, 1945 esaaeses IN V EN TOR SIDNEY 5. PIC/(LES KZ-;;,

ATZWM Patented Oct. 10, 1950 BEACON ANTENNA SYSTEM Sidney B. Pickles,Jackson Heights, N. Y., assignor to Federal Telephone & RadioCorporation, New York, N. Y., a corporation of Delaware ApplicationMarch 19, 1945, Serial No. 584,596

This invention relates to antenna systems and more specially to antennasystems for use in directive radio systems such as localizing, guiding,beacon systems and the like.

A principal object is to provide an improved antenna arrangement forcontrolling the field of radiation and non-radiation in a desireddirection or directions.

The invention is in the nature of an improvement upon the antennaarrangement disclosed in my copending application, Serial No. 580,674,filed March 2, 1945. There is disclosed in that application a radiatingbeacon system wherein the directive antenna proper is provided with aspecial form of radiation shield and reflector whereby the directiveradiated field pattern can be given one or more minimum field intensityregions which can be directed at desired angles without materiallyaffecting the main directed beam action of the antenna.

Accordingly, it is another principal object of this invention to providea novel radiation screen for directed beacon antennae, whereby thedesired directive minima may be produced in the radiation pattern, whileat the same time providing greater sharpening to the main directivebeacon field.

A feature of the invention relates to a radiation screen for beaconantennae and the like wherein the screen is provided with a novelarrangement for terminating the ends of the screen to achieve improveddirectivity and field pattern control.

Another feature relates to a radiation screen for beacon antennae andthe like comprising a series of screen conductors mounted in spacedarray and with respect to the beacon antenna. These conductors havenovel terminating means to render them substantially aperiodic at thebeacon working frequencies.

A further feature relates to a radiation screen for antennae, comprisinga wire network. which is provided with a series of auxiliary radiationabsorption units for preventing standing waves in the main body of thescreen at the antenna working frequencies, and without the necessity ofemploying relatively long terminating wires which approach the earth.

A further feature relates to a radiation screen for antennae, comprisinga series of spaced superposed conductors whose ends are space-coupled toindividual radiation absorbing terminal units to terminate saidconductors in their characteristic impedances.

7 Claims. (01. 250-3s.5)

A further feature relates to a bi-part reflecting screen for antennae,comprising a main series of spaced reflector conductors and an auxiliaryseries of reflector conductors for controlling the resonancecharacteristics of the said main conductors at the antenna workingfrequencies.

A still further feature relates to a reflecting screen for antennae,comprising a series of spaced reflector conductors having theirconfiguration designed to provide a terminating impedance equivalent totheir characteristic impedance and without the necessity of employingextensive terminating wires for that purpose.

Other features and advantages not particularly set forth will beapparent after a consideration of the following detailed descriptionsand the appended claims.

Inasmuch as the invention finds its primary utility in connection with aradio beacon system of the kind disclosed in said application, SerialNo. 580,674, only those parts of an antenna and reflecting system willbe described herein as are necessary to an understanding of theinventive concept. It will be understood however, that the disclosure ofsaid application Serial No. 580,674 is to be taken, by reference, aspart of the present disclosure.

In the drawing which shows certain preferred modes of practicing theinvention:

Fig. 1 is a plan view of an antenna array and reflector-shieldarrangement embodying principles of the invention.

Fig. 2 is a front elevation view of Fig. 1.

Fig. 3 is an elevational view showing a modification of Figs. 1 and 2.

Referring to Figs. 1 and 2, there is shown a series of horizontal loopantennae l, which may be supported in any suitable manner to provide thewell-known broadside antenna array whereby a directed radiation field isproduced. While the drawing shows a series of five antenna units, itwill be understood that a greater or less number may be employed.Further, while the antennae are shown as of the loop type, any otherwell-known directive antenna units may be employed.

Suitably mounted rearwardly of the antenna, is a reflector-shield orscreen comprising a series of spaced conductors 2, insulatingly mountedon posts 3 and 4. The distance D between the screen and the antennaarray is preferably made one-half wave length or greater, while thelength L of the screen may be from 4 to 8 wave lengths so as to providethe required shielding action rearwardly of the antennae. The wires 2may be strung between poles 3 and 4, so as to be relatively close toeach other, depending of course upon the particular screening andreflecting actions desired.

For the purpose of controlling the radiation resonance of the screen,and particularly so that no standing waves will be set up therein at theoperating antenna frequencies, I have found that the individual wires 2should be terminated at their ends so that their terminating impedancesubstantially matches the impedance of the wires proper. In my priorapplication Serial No. 580,674 this result has been achieved byextending the individual wires 2 asymptotically towards the earth. Inorder to achieve the necessary impedance with this prior arrangement,considerable ground area is required for the extended terminating wires.However, I have found that the desired results can be achieved withoutthese relatively long extensions on the wires 2. For this purpose, thereare mounted adjacent the ends of the wires 2, corresponding auxiliaryscreen members 5, 9, which can be insulatingly supported in anywell-known manner on suitable posts 'i, 8. Each of the members 5, 6, maybe in the form of a single straight conductor preferably of a half wavelength, and each is mounted in front of a corresponding wire 2 of themain screen. The spacing and location of the wires 5 with respect towires 2, can be varied to provide the desired phase and coupling ratiotherebetween so as to achieve the desired impedance termination for themain screen wires. While the drawing shows the wires 5 displacedvertically with respect to the associated wires 2, it will be understoodthat, if desired, each wire 5 may be mounted in the same plane as theassociated wire 2, or if desired, they may be mounted at any suitableangle with respect thereto.

It will be understood of course that, in accordance with acceptedcoupled section theory, the correct phasing to achieve the desiredterminating impedance will be a function of the length L of the mainscreen and the coupling between the wires 2 and 5. It can be shown thatthe tightest coupling will be obtained when the main section wires 2extend one-quarter wave length beyond the ends of auxiliary wires 5.

I have found that with the foregoing described arrangement, theauxiliary wires 5 have considerable directional properties, and whenthey are excited under control of the wires 2, they act as auxiliaryradiators and therefore may be used to add small amounts of energy onthe directed field pattern from the antenna I, thus giving additionalcontrol over the sensitivity and shape of the field pattern. It will beunderstood that while the drawing shows the auxiliary wires at each endof the screen equal in number to the main wires 2, one or more of theseauxiliary wires may be deleted in order to produce special efiect on thefield pattern.

Referring to Fig. 3, there is shown a modification of Figs. 1 and 2 forobtaining substantially the same results. Instead of controlling theterminating impedance of the wires 2 through the intermediary ofseparate spaced coupled radiator sections 5, this control may beeffected without such separate members or in addition thereto. Thus, asshown in Fig. 3, the wires 2, instead of proceeding directly to theirends, are provided adjacent those ends with bent or partially loopedsections 9 and 10. These sections 9 and I!) may be in the form of halfloops. In effect therefore, the semi-loops 9 and I0 provide aquasi-discontinuity in the propagation characteristics of the wires 2along their lengths, and the sections 9 and I0 perform substantially thesame function as though the wires 2 (Fig. 1) had each a semi-loopconductor inserted therein from the back of the screen. In other words,the current propagated towards the screen terminations will flow aroundthe bent sections 9 and H] which will cause the latter to act asauxiliary radiators. The phase of the radiation from these auxiliaryradiators will, in accordance with accepted theory, be a function of thelocation of the bends along the length of the wires 2 and their locationwith respect to the antennae l, as well as a function of the impedancepresented by the sections 9 and I0 themselves. While Fig. 3 shows thesections 9 and I0 offset in a vertical plane from the wires 2, it willbe understood that these offset sections may be madein any other desiredplane.

While certain particular embodiments have been disclosed herein, variouschanges and modifications may be made without departing from the spiritand scope of the invention. The examples given in the drawing are merelyillustrative and not by way of limitation on the scope or utility of theinvention.

What is claimed is:

1. An arrangement for controlling the radiation pattern of an antenna,comprising a radiation screen made of a series of horizontal wiresmounted in spaced relation to the antenna, and means to control theaperiodicity of said screen at the antenna working frequencies, thelastmentioned means comprising screen terminating impedance meansspace-coupled to the extremities of said screen wires.

2. An arrangement for controlling the radiation pattern of an antenna,comprising a radiation screen made of a series of horizontal wiresmounted in rearward spaced relation to the antenna, and means toterminate said screen in its characteristic impedance, thelast-mentioned means comprising an auxiliary screen spacecoupled to theextremities of said radiation screen wires.

3. In combination, a directional antenna, a conductive network mountedrearwardly of said antenna and comprising a series of elongated spacedconductors, an impedance terminating means for said conductorscomprising another series of short conductors mounted inradiationcoupled relation to the ends of said elongated conductors.

4. The combination according to claim 3 in which said elongatedconductors are approximately 4 to 8 times the operating wave length ofthe antenna, and said short conductors are approximately one-half saidwave length.

5. The combination according to claim 3 in which said ends of theelongated conductors extend beyond said short conductors byapproximately one-quarter wave length.

6. In combination, a directional antenna, a conductive network mountedrearwardly of said antenna, said network comprising a first series ofspaced horizontal wires and a second series of spaced horizontal wiresmounted in spacecoupled relation to the end sections of the firstseries, the length of said second series of wires and their spacing withrelation to the first series and with relation to said antenna beingproportioned to render said network substantially aperiodic at theantenna operating frequencies.

7. The combination according to claim 6 in which said first series ofWires are mounted at least one-half wave length rearwardly of theantenna and said second series have a length approximately one-half theoperating Wave 5 length of the antenna.

SIDNEY B. PICKLES.

REFERENCES CITED The following references are of record in the 10 fileof this patent:

Number 6 UNITED STATES PATENTS Name Date Hahnemann June 17, 1930 CarterJune 11, 1940 Alford Dec. 31, 1940 Gavitt May 12, 1942 NumberSchelkunoff et al. Aug. 4, 1942 FOREIGN PATENTS Country Date France Mar.2, 1931

